Demonstrators gathered in Chicago to protest against the death of a black teenager shot by a white police officer, an incident captured on video that President Barack Obama called "deeply disturbing".

About two dozen people gathered outside Mayor Rahm Emanuel's City Hall office, a day after the release of a graphic squad-car video showing the officer shooting 17-year-old Laquan McDonald 16 times.

The officer, Jason Van Dyke, was charged with first-degree murder.

The group held banners showing photos of other black people fatally shot by police in Chicago and elsewhere.

Several protesters said they were parents of black men who were killed by Chicago officers.

"You cannot kill our children and expect us to be quiet any longer," Quovadis Green said. "It is unacceptable."

A number of police killings of black men over the past year have given rise to the nationwide "Black Lives Matter" movement, pushing the issue to prominence during the 2016 presidential campaign.

Mr Obama said he is asking Americans to "keep those who've suffered tragic loss in our thoughts and prayers" this Thanksgiving "and to be thankful for the overwhelming majority of men and women in uniform who protect our communities with honour".

The president said he is personally grateful to the people of his home town - Chicago - for keeping protests peaceful.

One of her rivals, Senator Bernie Sanders, said all Americans "should be sickened" by the video.

Activist Mark Carter called on supporters to "rise up" and shut down the Magnificent Mile shopping area on Friday - the day after the Thanksgiving holiday when people traditionally flock to stores to take advantage of discounts.

He said protesters also planned to target the Board of Trade and other landmarks in the coming days.

Mr Carter and others want the Department of Justice to investigate the Chicago Police Department and its history of covering up bad behaviour.

The Urban League of Chicago joined in the call for an investigation, alleging a pattern of "discriminatory harassment" against black people.